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Microsiphoniella [Macrosiphini]Microsiphoniella are rather small aphids, distinguishable from the closely related European genus Microsiphum by having much longer dorsal hairs. The antennal tubercles are weakly to modestly developed. The antennal terminal process is at least 3 times the base of antennal segment VI. Both apterae and alatae have secondary rhinaria on antennal segment III. The apical rostral segment is conical, with the sides concave to stiletto-shaped. The siphunculi are small and short, not longer than wide, or less than or equal to 0.5 times the caudal length. The cauda is broadly triangular. There are four Microsiphoniella species, all monoecious holocyclic on different species in the genera Seriphidium and Artemisia (tribe Anthemidae, family Asteraceae). All species are restricted to the USA. Microsiphoniella acophorum (Brownish-black microsiphon aphid) Western USAAdult apterae of Microsiphoniella acophorum are pear-shaped, shiny brownish black to black. A dark patch on the dorsum is apparent in cleared specimens. The antennae are dark beyond the basal two-thirds of segment IV. The terminal process is 3.1-4.5 times the base of antennal segment VI (cf. Microsiphoniella artemisiae, which has the terminal process 4.7-6.3 times the base of that segment). Antennal segment III bears 1-4 secondary rhinaria. The rostrum reaches the first abdominal segment. The apical rostral segment (RIV+V) is 0.12-0.14 mm long, and not more than twice the diameter of the rhinaria. Dorsal abdominal hairs are fine-pointed, or blunt and spine-like, and not more than twice as long as the basal diameter of antennal segment III (cf. Microsiphoniella oregonensis, which has thick dorsal abdominal hairs, 2-3 times longer than the basal diameter, with expanded or fan-shaped apices). The femora are dark or dusky, especially the middle and hind pairs, but the tibiae are mainly pale. The siphunculi are pale, very short, and hardly longer than their basal widths. The cauda is broader than long, tapering, and bears numerous hairs. The body length of adult Microsiphoniella acophorum apterae is 1.0-1.5 mm.
Images above copyright Andrew Jensen, under a creative common licence. The alate Microsiphoniella acophorum (not pictured) is black, with dark antennae. Antennal segment III bears 5-6 secondary rhinaria. The siphunculi are cylindrical or slightly broader at their base, smooth and with a flange. The cauda is tapering, acute, shorter than broad, and bears 2 pairs of lateral hairs. Microsiphoniella acophorum is monoecious holocyclic on the stems and leaves of big sagebrush (Artemisia (= Seriphidium) tridentata) and long-leaved sage (Artemisia longifolia). Oviparae and alate males occur in September-October. The species is found in the western USA.
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